The principal objectives of this research and the methods that will be used to achieve them are: 1) Determine the nature of the aggregation and ligation interactions between the components of photosynthetic reaction centers (RC) and subunits (PSU) using resonance Raman spectroscopy (RRS); 2) Determine the effect of these interactions and electrode adsorption interactions (viz., spontaneous chemisorption and/or covalent surface modification) on the electrochemical properties of RC and PSU components using cyclic voltammetry, ac polarography, and chronocoulometry; and 3) Develop a new method of probing the dynamics of photosynthetic electron transfer (ET) reactions using time-resolved RRS (TR3S) and using the RRS of in vitro electrogenerated radical ions (i.e., RRSE) to provide the data base for the interpretation of the TR3S. The significance of this proposed research is two-fold: 1) the data that will be acquired by applying RRS and electrochemical methods separately to photosynthetic species will provide new mechanistic insight into how intermolecular interactions in RCs and PSUs determine ET pathways; and 2) the combined application of TR3S and RRSE will provide unprecedented molecular specificity for the in vivo study of electron transfer induced structure changes in photosynthesis as well as other biological systems. A more speculative but perhaps more significant outcome might be the development of a new class of synthetic RC models based on the structure data provided by RRSE studies of photosynthetic pigments covalently attached to electrode surfaces.